JPH0933947A - Active matrix substrate and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain excellent display quality by improving the aperture rate of a liquid crystal display device and preventing leakage between a pixel electrode and a source electrode. SOLUTION: On an insulating film 10 formed on a scanning line 2 and a signal line 3, the pixel electrode 13 formed of a transparent conductive film and a light shield film 12 formed of a metallic thin film are laminated in this order from a substrate side. The insulating film 10 prevents a leak between the scanning line 2 and the signal line 3, and the pixel electrode 13 and the light shield film 12 improves the contrast, prevents a TFT from deteriorating, and further improves the aperture rate. The pixel electrode 13 is formed between those insulating film 10 and light shield film 12, so the transparent conductive film functions as an etching stop layer when the metallic thin film is etched, so that the excellent insulating film 10 which has no deterioration can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an active matrix substrate used in, for example, a liquid crystal display device, in which a non-linear element such as a thin film transistor is formed as a switching element in a matrix, and a method for manufacturing the same.

[0002]

2. Description of the Related Art In recent years, OA (office automation) devices such as notebook personal computers and AV (audiovisual) devices are required to have low power consumption. Along with this, liquid crystal display devices (LCD) used for them, particularly active matrix liquid crystal display devices (AM-LCD), are strongly required to have low power consumption.

In the AM-LCD, a liquid crystal is provided between an active matrix substrate having a pixel electrode and a switching element for selectively driving the pixel electrode formed on a matrix, and a counter substrate having a counter electrode. Has a sandwiched structure. Non-linear elements such as a thin film transistor (TFT) element, a MIM (metal-insulating layer-metal) element, a MOS (metal-oxide-silicon) transistor element, a diode and a varistor are generally known as the switching element.

An effective means for reducing the power consumption of this AM-LCD is to improve the aperture ratio. As a technique for improving the aperture ratio of AM-LCD,
Pixel on Pass (configuration in which the pixel electrode is formed above the wiring and the switching element via the interlayer insulating film)
There is. As a conventional Pixel on Pass structure, one shown in FIG. 3 is known (Japanese Patent Laid-Open No. 5-100).
250). In this liquid crystal display device, a gate wiring 13, a source wiring 17, and a planar TFT 12 as a switching element for a pixel are provided on an insulating substrate 26 on the lower side of the drawing, and an interlayer insulating film 37 and a pixel electrode are provided above the gate wiring 13. 11
And an active matrix substrate in which are formed.

The planar type TFT 12 has a semiconductor layer 14 as the lowermost layer. This semiconductor layer 14 is two-dimensionally
Source / channel / drain are formed, the conductive film 34 and the source wiring 17 are connected to the source / drain 22a, 22b, and the gate electrode 16 is formed on the channel via the gate insulating film 15. The contact between the drain and the pixel electrode 11 is made by using the conductive film 34 and the conductive light shielding film 25 on the conductive film 34. An insulating light-shielding film 42 is formed on the pixel electrode 11 so as to cover the TFT 12. Incidentally, 33 and 35 in the figure are interlayer insulating films, and 23 is a storage capacitance line.

[0006]

By the way, in the above-mentioned conventional active matrix substrate, the light shielding film 2 is used.
When etching 5 and 42, there is a problem that the interlayer insulating films 37, 33 and 35 as protective films provided on the lower side of each deteriorate. This problem occurs regardless of whether the wet etching method or the dry etching method is used. This also occurs in planar type and inverted stagger type TFTs, MIM elements and the like.

When a wet etching method is used, when a film defect occurs due to a hole formed by dust or peeling of the film in the step of forming a protective film, the etching liquid permeates into the film defect and further the film is formed. The defect expands. On the other hand, when the dry etching method is used, T which is the material of the light shielding film 25 is used.
Regarding i and the like and SiN _{x and the} like as the material of the protective film, the etching rate of SiN _{x and the} like is higher than the etching rate of Ti and the like, and there is no etching rate selection ratio between them. Therefore, the protective film is largely etched before the etching of the light shielding film is completed. As a result, it becomes difficult to manufacture an active matrix substrate.

The above-mentioned problem is caused by T as a material of the light shielding film.
Instead of i, aluminum (Al) or molybdenum (M
o), Ta, etc. cannot be solved. For example, in fluorine-based dry etching, Ti, Al, Mo, T
Among metal films such as a, T has the highest etching rate.
a film. If the etching rate of the Ta film is 1,
The etching rate of SiN _x , which is the material of the protective film, is about 3
That is, the selectivity of the Ta / SiN _x etching rate is 0.3. With other metal films such as Ti, Al, and Mo, the selection ratio of the etching rate becomes smaller. As a result, Al, Mo, instead of Ti, was used as the material of the light shielding film.
Even if Ta or the like is used, the protective film is largely etched before the etching of the light shielding film is completed. Even when TaN is used as the light shielding film, the same problem occurs because the TaN / SiN _x etching rate selection ratio is about 0.3.

When a liquid crystal display device is manufactured using such an active matrix substrate having a deteriorated protective film, point defects occur due to leakage between the source wiring and the pixel electrode, resulting in a serious display quality defect. Becomes Also, Japanese Unexamined Patent Publication No.
In No. 100250, in addition to the light-shielding film at the contact portion, another light-shielding film is formed on the picture element, but this is not preferable because the number of processes is increased.

The present invention has been made to solve the problems of the prior art, and the aperture ratio can be improved by the light shielding film, and the insulating protective film can be formed without deterioration to form a pixel electrode. It is an object of the present invention to provide an active matrix substrate which can prevent leakage from the source electrode and which does not increase the number of processes, and a manufacturing method thereof.

[0011]

In the active matrix substrate of the present invention, a plurality of scanning lines and a plurality of signal lines are formed so as to intersect each other on an insulating substrate, and each of them is surrounded by the scanning lines and the signal lines. An active matrix substrate in which a pixel electrode and a non-linear element for driving each pixel electrode are arranged in a matrix in a region, and formed by covering the scanning line, the signal line and the non-linear element. A transparent conductive film, which is the pixel electrode, is provided on the transparent insulating film in a state of being electrically connected to an electrode of the nonlinear element through a contact hole provided in the transparent insulating film. A light shielding film made of a metal thin film is provided on the film to cover the nonlinear element,
Thereby, the above object is achieved.

In the active matrix substrate of the present invention, the pixel electrode is a single layer film made of any one material of tin oxide, indium oxide, and indium tin oxide, or a multilayer film made of two or more materials. The light shielding film may be a single layer film made of any one material of molybdenum, aluminum, titanium, tantalum and tantalum nitride, or a multilayer film made of two or more materials. .

According to the method of manufacturing an active matrix substrate of the present invention, a plurality of scanning lines and a plurality of signal lines are formed on an insulating substrate so as to intersect with each other, and an image is formed in each region surrounded by the scanning lines and the signal lines. A method for manufacturing an active matrix substrate in which element electrodes and non-linear elements for driving each picture element electrode are arranged in a matrix, the method covering the scanning lines, the signal lines and the non-linear elements, and A step of forming a transparent insulating film on the electrode of the non-linear element in a state having a contact hole, and a two-layer film comprising a transparent conductive film for a pixel electrode and a metal thin film for a light shielding film on the transparent insulating film Forming the transparent conductive film on the substrate side and electrically connecting the transparent conductive film to the electrode through the contact hole; and the metal thin film above the two-layer film. Etching the nonlinear Forming a light shielding film covering the child, and forming a pixel electrode by etching the lower transparent conductive film of the two-layer film, the object is achieved.

The operation of the present invention will be described below.

In the present invention, a pixel electrode made of a transparent conductive film and a light shielding film made of a metal thin film are laminated in this order on the insulating film formed on the scanning line and the signal line from the substrate side. There is.

Therefore, the insulating film formed under the pixel electrodes prevents leakage between the scanning lines and the signal lines and the pixel electrodes. Further, the light shielding film can improve the contrast and prevent the deterioration of the TFT, and further improve the aperture ratio. Since the pixel electrode is formed between the insulating film and the light shielding film, the transparent conductive film functions as an etching stop layer of the insulating film when the light shielding film made of a metal thin film is etched,
As a result, a good insulating film without deterioration can be obtained. Also,
There is no increase in the number of processes because no extra light shielding film is required.

[0017]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a plan view showing two picture elements of an active matrix substrate which is an embodiment of the present invention.
2 is a sectional view taken along the line AA ′ of FIG. The picture elements on the left side of FIG. 1 are shown so that the TFT structure under the light shielding film can be seen.

This active matrix substrate is formed on a glass substrate 1 with a gate wiring 2 made of Ta and a source wiring 3 made of Ti intersecting each other. Gate wiring 2
In the vicinity of the intersection of the source line 3 and the pixel electrode 13,
And the TF connected to the gate wiring 2 and the source wiring 3.
T20 is formed for each picture element.

In the TFT 20, the first gate insulating film 4 made of Ta ₂ O ₅ is formed so as to cover the gate electrode 2a which is a part of the gate wiring 2 arranged on the glass substrate 1, and on which the first gate insulating film 4 is formed. A second gate insulating film 5 made of SiN _x is formed so as to cover the entire surface of the substrate. A is formed on the second gate insulating film 5 so as to partially overlap the gate electrode 2a.
A semiconductor layer 6 made of —Si (i) is formed, and an etching stopper layer 7 made of SiN _x is formed on the central portion thereof.

A contact layer 8 made of a-Si (n ⁺ ) is formed on the semiconductor layer 6 while being separated on the etching stopper layer 7. A source electrode 3a that is a part of the source wiring 3 is formed so as to cover one side (right side in the drawing) of the contact layer 8, and a drain electrode 9 made of Ti is formed so as to cover the other side (left side in the drawing) of the contact layer 8. There is.

The drain electrode 9, including the TFT 20,
A protective film 10 made of a transparent insulating film such as SiN _x is formed so as to cover the source wiring 3 and the opening of the picture element. A contact hole 11 is formed in the protective film 10 so as to reach the drain electrode 9. A picture element electrode 13 made of ITO is formed on the protective film 10 so as to cover the opening of the picture element, and the picture element electrode 13 is connected to the drain electrode 9 through the contact hole 11. . A light shielding film 12 is formed on the pixel electrode 13 so as to cover the TFT 20.

This active matrix substrate is manufactured as follows.

First, a film thickness of 500 to 500 is formed on the glass substrate 1.
A 5000 angstrom Ta film is deposited by a sputtering method, and a pattern is formed by a photolithography method and etching is performed to form the gate wiring 2 including the gate electrode 2a. The etching of the Ta film includes a method of performing dry etching by plasmaizing a mixed gas of CF ₄ and O ₂ , and a method of performing wet etching using a mixed solution of hydrofluoric acid and nitric acid as an etching solution. When performing wet etching, a Ta ₂ O ₅ film having a film thickness of 1000 to 10000 angstrom is formed in advance between the glass substrate 1 and the Ta film to prevent the glass substrate 1 from being etched. Then, the surface of the gate wiring 2 is anodized so that the film thickness becomes 500 to 5
A Ta ₂ O ₅ film having a thickness of 000 Å is formed to serve as the first gate insulating film 4.

Subsequently, by plasma CVD, the SiN _x layer having a film thickness of 500 to 6000 angstroms to be the second gate insulating film 5 and the film thickness of the semiconductor layer 6 to be 50 are formed.
An a-Si (i) layer of 0 to 1000 angstroms,
A SiN _x layer to be the etching stopper layer 7 is continuously deposited in this order. After that, patterning is performed by a photolithography method, and the uppermost SiN _x layer is subjected to BHF.
By etching with (hydrofluoric acid + ammonium fluoride), only the etching stopper layer 7 is formed.

Next, a film having a thickness of 200 to 2000 angstroms to form the contact layer 8 is formed on the substrate in this state.
-Si (n ⁺ ) layer is deposited, and the a-Si (n ⁺ ) layer and the a-Si (i) layer are simultaneously patterned into an island shape by photolithography and etching,
The contact layer 8 and the semiconductor layer 6 are used.

After that, a film thickness of 500 to 50 is formed on the substrate.
A metal thin film is formed by depositing Ti having a thickness of 00 angstrom by a sputtering method, and the metal thin film is patterned by a photolithography method and then etched to form the source wiring 3 and the drain electrode 9 including the source electrode 3a.

Next, a SiN film having a thickness of 500 to 6000 Å is formed as a protective film 10 on the substrate.
_x film, that is, a transparent insulating film is deposited. After that, patterning is performed by a photolithography method, and etching is performed with BHF to form a contact hole 11 in the protective film 10.

Next, a single-layer film made of any one of ITO, SnO ₂ and InO ₃ or a multi-layer film made of two or more materials, for example, a film thickness of 300 to 300.
A transparent conductive film to be the pixel electrodes 13 is formed by applying a sputtering method so as to have a thickness of 0 angstrom.

Next, on the transparent conductive film, Ti, T
a single layer film made of any one material of a, TaN, Mo and Al or a multilayer film made of two or more materials is deposited by a sputtering method so as to have a film thickness of 500 to 5000 angstrom, A metal thin film to be the shielding film 12 is formed. Subsequently, after patterning this metal thin film by a photolithography method, the light shielding film 12 is formed by etching. There are two types of this etching method, a wet etching method and a dry etching method.

In the dry etching method, a parallel plate type dry etching apparatus having electrodes opposed to each other is used, and a fluorine-based mixed gas, for example, a mixed gas of CF ₄ and O ₂ gas, or a chlorine-based mixed gas, for example CCl. The mixed gas of ₄ and O ₂ gas is turned into plasma to etch the metal thin film. For example, when the etching rate of the Ta film that is the material of the metal thin film is 1, the etching rate of ITO that is the transparent conductive film is 0.1 times or less, and Ta / ITO
The etching rate selection ratio is 10 or more. Therefore, the transparent conductive film is not etched before the etching of the metal thin film is completed, and the protective film 10 formed under the transparent conductive film is not etched. T
Metal thin film materials other than a, Ti, TaN, Mo and Al
The same applies to other materials such as transparent conductive film materials other than ITO, SnO ₂ and InO ₃ .

In the wet etching method, HF and HNO are used.
Etching of the metal thin film is performed with a hydrofluoric / nitric acid-based mixed etching solution such as a mixture with ₃ . With a nitric acid-based etching solution that etches metal thin films and Si-based materials,
The ITO is hardly etched. Therefore, the transparent conductive film is not etched before the etching of the metal thin film is completed, and the protective film 10 formed under the transparent conductive film is not etched. The same applies to a transparent conductive film material other than ITO, SnO ₂ and InO ₃ .

Finally, the transparent conductive film is patterned by a photolithography method and etched to form a pixel electrode 13. In this etching,
By using a ferric chloride-based etching solution such as a mixed solution of HCl and FeCl ₃ , a hydrogen bromide-based etching solution such as HBr, or a mixed etching solution of HCl and Zn, only the transparent conductive film is etched. With these etching solutions, only the transparent conductive film can be etched without etching SiN _x, which is the material of the protective film 10.

In the active matrix substrate of this embodiment, the transparent conductive film covers the protective film 10 when the light shielding film 12 is etched.
Is not impaired. As a result, the insulating property between the source wiring 3 and the etching 13 can be improved.

A liquid crystal display device formed by disposing a counter substrate having a counter electrode formed on the surface of the active matrix substrate and enclosing a liquid crystal between the two substrates is caused by deterioration of the protective film 10. It is possible to reduce the probability of the occurrence of point defects, and to significantly improve the display quality.

Although the SiN _x film is formed as the protective film in the above embodiment, other materials can be used. For example, Si
A transparent insulating material such as O ₂ can be used. Also, the protective film 1
0 does not necessarily have to be transparent, and an insulating film that is not transparent can be used. Although the active matrix substrate in which the TFT is formed as the switching element has been described in the above embodiment, the present invention is not limited to this, and an active element using a nonlinear element such as a MIM element, a MOS transistor element, a diode or a varistor as a switching element. It can also be applied to a matrix substrate.

[0037]

As is apparent from the above description, according to the present invention, in order to prevent the leak between the scanning line and the signal line and the pixel electrode and improve the aperture ratio, the pixel is formed on the insulating protective film. Since the electrode and the light shielding film are formed, it is possible to prevent deterioration of the insulating protective film and improve the insulating property. Therefore, when used in a liquid crystal display device, the probability of occurrence of point defects due to deterioration of the protective film can be reduced. As a result, the display quality of the liquid crystal display device can be significantly improved, and the manufacturing yield can be significantly improved. Moreover, since no extra light shielding film is required, the number of processes is not increased.

[Brief description of drawings]

FIG. 1 is a plan view showing two picture elements of an active matrix substrate which is an embodiment of the present invention.

FIG. 2 is a sectional view taken along the line A-A ′ in FIG.

FIG. 3 is a cross-sectional view showing a conventional active matrix substrate.

[Explanation of symbols]

 1 Glass Substrate 2 Gate Wiring 3 Source Wiring 4 First Gate Insulating Film 5 Second Gate Insulating Film 6 Semiconductor Layer 7 Etching Stopper Layer 8 Contact Layer 9 Drain Wiring 10 Protective Film 11 Contact Hole 12 Light Shielding Film 13 Picture Element Electrode

Claims (3)

[Claims] 1. A plurality of scanning lines and a plurality of signal lines are formed to intersect each other on an insulating substrate, and a pixel electrode and each pixel electrode are provided in each region surrounded by the scanning line and the signal line. A non-linear element for driving is an active matrix substrate arranged in a matrix, and the pixel electrode is provided on an insulating film formed to cover the scanning line, the signal line and the non-linear element. A transparent conductive film is provided in a state of being electrically connected to an electrode of the non-linear element through a contact hole provided in the insulating film, and further comprises a thin metal film covering the non-linear element on the transparent conductive film. An active matrix substrate provided with a light shielding film. 2. The pixel electrode is a single layer film made of any one material of tin oxide, indium oxide, and indium tin oxide or a multilayer film made of two or more materials, and the light shielding element The active matrix substrate according to claim 1, wherein the film is a single-layer film made of any one of molybdenum, aluminum, titanium, tantalum, and tantalum nitride, or a multilayer film made of two or more materials. 3. A plurality of scanning lines and a plurality of signal lines are formed to intersect each other on an insulating substrate, and a pixel electrode and each pixel electrode are provided in each region surrounded by the scanning line and the signal line. A method for manufacturing an active matrix substrate in which a non-linear element for driving is arranged in a matrix, the scan line, the signal line and the non-linear element being covered, and
A step of forming an insulating film in a state having a contact hole on the electrode of the nonlinear element; and a two-layer film composed of a transparent conductive film for a pixel electrode and a metal thin film for a light shielding film on the insulating film. Forming the transparent conductive film on the substrate side and electrically connecting the transparent conductive film and the electrode through the contact hole; and forming the metal thin film above the two-layer film. A method of manufacturing an active matrix substrate, comprising: a step of etching to form a light shielding film covering the non-linear element; and a step of etching the transparent conductive film below the two-layer film to form a pixel electrode. .